Charlie Qiangeng Xu created HBASE-17039: -------------------------------------------
Summary: SimpleLoadBalancer schedules large amount of invalid region moves Key: HBASE-17039 URL: https://issues.apache.org/jira/browse/HBASE-17039 Project: HBase Issue Type: Bug Components: Balancer Affects Versions: 1.2.3, 1.1.6, 2.0.0 Reporter: Charlie Qiangeng Xu Assignee: Charlie Qiangeng Xu Fix For: 2.0.0, 1.2.3, 1.1.6 After increasing one of our clusters to 1600 nodes, we observed a large amount of invalid region moves(more than 30000 thousand moves) fired by balance chore. Thus we simulated the problem and printed out the balance plan, only to find out many server that had two regions for a certain table(we use by table strategy), sent out both regions to other two servers that have zero regions. In the SimpleLoadBalancer's balanceCluster function, the code block that determines the underLoadedServers might have a problem: if (load >= min && load > 0) { continue; // look for other servers which haven't reached min } int regionsToPut = min - load; if (regionsToPut == 0) { regionsToPut = 1; } if min is zero, some server that has load of zero, which equals to min would be marked as underloaded, which would cause such problem mentioned above. Since we increase the cluster's size to 1600+, many table only have 1000 regions, now would encounter such issue. -- This message was sent by Atlassian JIRA (v6.3.4#6332)